Stability of phase H in the MgSiO4H2-AlOOH-SiO2system
Stability of phase H in the MgSiO4H2-AlOOH-SiO2system
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DOI：
10.1016/j.epsl.2017.01.033
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发表时间：
2017-04-01
影响因子：
5.3
通讯作者：
Caracas, Razvan
中科院分区：
文献类型：
--
作者：
Panero, Wendy R.;Caracas, Razvan
新发现的含水相H MgSiO4H2对地球下地幔的压力和温度是稳定的，表明地球下地幔可能参与了水的循环。本文给出了在20 ~ 60GPa的h - δ aloh - sio(2)相体系中该相稳定性的初始计算结果，探索了该矿物的宽压力-温度稳定场。我们发现，在所有压力下，H相中的氢都在单孔中键合，只有纯相的氢会产生压力诱导的对称，而固溶体在高压下保持不对称键合。此外，SiO(2)中少量的Al + H使SiO(2)的cacl2结构在低至20GPa的压力下保持稳定，而H相和δ AlOOH在所有压力下都能形成理想的混合物。相对于地球下地幔的无水组合，其结构稳定度为16-19kJ/mol。在富铝的H相中，相对于纯物质，这使矿物的稳定性提高了800K，使其在沿典型地热的较低地幔温度下具有潜在的稳定性。(C) 2017 Elsevier b.v.版权所有
The newly described hydrous phase H, MgSiO4H2, is stable to the pressures and temperatures of the Earth's lower mantle, suggesting that the Earth's lower mantle may participate in the cycling of water. We present the results of ab initiocalculations on the stability of this phase within the phase H-delta AlOOH-SiO(2)system between 20 and 60GPa, exploring the wide pressure-and temperature stability field of this mineral. We find that hydrogen in phase H is bonded in a single well at all pressures, and only the pure phase results in pressure-induced symmetrization, while the solid solution maintains asymmetric bonding to high pressure. Substitutions on octahedral sites are locally charge-balanced by H. Furthermore, small amounts of Al + H in SiO(2)stabilize the CaCl2-structure of SiO(2)to pressures as low as 20GPa while phase H and delta AlOOH form an ideal mixture at all pressures considered. The resulting structure is stable relative to the anhydrous assemblage of the Earth's lower mantle by 16-19kJ/mol. In alumina-rich phase H this increases the stability of the mineral by similar to 800K relative to the pure substance, making it potentially stable under lower mantle temperatures along typical geotherms. (C) 2017 Elsevier B. V. All rights reserved.